Hi devs,
some months ago I announced my History Splitter and the availability of
extracts. In the last months I've completed my work and implemented a
second cutting-algorithm. While the --hardcut algorithm will stay the
default as a, the --softcut algorithm features the following attributes:
- version-completeness (if one version is inside the bbox, all versions
are included in the extract)
- way-completeness (ways are not cropped but included as they are in the
database)
- way-reference-completeness (all nodes of ways touching the bbox are
included)
- relation-completeness (relations are not cropped, they may however
have children which are not included inside the extract)
- cascading-relations (all super-relations of relations touching the
bbox are included in the extract)
those features are implemented using a two-pass process. It runs
single-threaded, so to use multiple cores you are required to run
multiple independent instances of the program. A python script that is
able to control this parallelization is included, however multiple
simultaneous splits increases the number of disk-seeks, which possibly
outruns the speedup gained through distributing the CPU-Load to multiple
cores.
The tool is, without changes, suitable for normal planet-extractions,
too. By choosing the sequence and parallelization carefully, it's
possible to accomplish the specific task of extracting a bbox or a
polygon in 1/3 of the time required by osmosis.
The source and building instructions are available at github:
https://github.com/MaZderMind/osm-history-splitter
If you have bug reports or problems compiling or running the splitter,
don't hesitate to mail me directly at [email protected].
Peter
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